Following a year that featured the lowest-rated season of American Idol ever, Fox's head of unscripted programming is on his way out.

After 18 years at Fox, Mike Darnell will step down as president of alternative entertainment at the end of June. The news will inevitably be met with much disappointment as Darnell's name has long been synonymous with the unscripted genre and the kind of risk-taking that success in the space demands. The decision to move on is said to be his.

"I’m extremely grateful that Fox has offered me a new long-term contract (and anyone who knows me won’t believe I’m saying this), but I’ve decided it’s time for a change. With my current deal ending in June, and having been here for 18 years (kind of a record in Hollywood), I had to make a decision: either stay (and basically admit to myself I was going to retire at Fox ... not a terrible choice) or leave and try something new. I’ve been in ‘Reality’ since before it was even called that, and it has truly been an amazing ride," Darnell said in a statement announcing the news Friday.

He continued: "However, the world has changed drastically over the last few years and now with hundreds of channels and limitless ways to watch television, I’ve decided this was the perfect time to take advantage of the rapidly changing marketplace. To say I am going to miss everyone here and that the people at FOX are like a family to me would be the understatement of the decade. I have so many people to thank (and I will call all of you!), but first and foremost, I want to thank Kevin Reilly, Peter Rice, Chase Carey and Rupert Murdoch for all their amazing support over these many years.”

During his tenure, Darnell oversaw the creation of American Idol -- TV's No. 1 series for nine consecutive seasons -- as well as unscripted entries including The X Factor, So You Think You Can Dance, MasterChef, Hell's Kitchen, Kitchen Nightmares and countless others that helped shape Fox. For many years, it was his bold and enviably broad programming --and the controversy that often accompanied it-- that propped up the network. In that tenure, he has amassed many fans in the producing community, thanks to his unabashed love of the genre and his willingness to take big risks even as the industry in which he operated grew increasingly risk-averse.

“Mike has been a trailblazer for the entire industry and has made innumerable contributions to the growth and success of the network over the past two decades," Fox Networks Group chairman Peter Rice said. "His passion for -- and dedication to -- television knows no bounds. He is like a member of the family, and Fox won’t be the same without him. While we wish he would’ve stayed forever, we regretfully accept his decision.”

Added Rupert Murdoch, chairman and CEO of News Corp. of the famously competitive exec who had a particularly long leash: “Mike took risks at a critical time and was a pioneering force in shaping the reality programming genre that exists today. He’s a smart and fearless executive who will be missed.”

But as Darnell noted, the landscape has shifted. At his network, alternative programming, long the bread and butter of Fox, went into something of a tailspin over the last season. Though American Idol remains a top-five broadcast, its massive 25 percent ratings decline during the last few months pushed the network's demo average for the season down 22 percent. The 2012-13 season marked the first time in over a decade that Fox didn't have top honors. The recently ended May sweep, which has seen Fox dominate every year since American Idol premiered, left the network tied for a modest first with ABC and CBS.

The X Factor also proved to be a disappointment, too. Despite digging deep into network pockets to bring Britney Spears onboard as a judge, the modest hit dropped 22 percent in its sophomore return. Other new launches haven't fared so well either. Last summer's dating series Take Me Out and The Choice both fizzled.

And while competitions drop and new launches fail to gain traction, Darnell has had a consistent performer in Gordon Ramsay. The chef, whose programming on the network increases to five series this fall, continues to dominate the culinary space on broadcast television. Fox on Thursday launched Darnell's latest entry, the layoff-themed Does Somebody Have to Go, which pulled a mediocre 1.3 rating in the target demographic against a night largely filled with repeats.